In general, a vehicle body frame structure for an all-terrain vehicle (hereinafter referred to as an “ATV”), wherein the vehicle body frame is of a bisected structure has been known.
Such is disclosed, for instance, in Japanese Patent Laid-open No. Sho 63-170176. FIG. 2 of Japanese Patent Laid-open No. Sho 63-170176 will be described referring to FIG. 8 below.
FIG. 8 is a perspective view of a conventional vehicle body frame structure for an ATV, in which a vehicle body frame 201 is composed of an upper vehicle body frame 202, a lower vehicle body frame 203 connected to a lower portion of the upper vehicle body frame 202, and cushion brackets 204 (only one on one side is shown) connected respectively to front portions of the upper vehicle body frame 202 and the lower vehicle body frame 203.
The upper vehicle body frame 202 is composed of a main frame 206, a left-right pair of center frames 207, 208 formed integrally with the main frame 206, a down tube 211 extended forwardly downwards from the front end of the main frame 206, a front member 212 extended downwards from a front portion of the down tube 211, and a back stay 213 extended downwardly rearwards from a rear portion of the down tube 211.
The lower vehicle body frame 203 is composed of a left-right pair of a left bottom frame 215 and a right bottom frame 216, and cross members 217, 218 disposed bridgingly between rear portions of the left bottom frame 215 and the right bottom frame 216.
The cushion bracket 204 is a member abutted on both side surfaces of a front vehicle body frame assembly 221 and welded at outer peripheral portions thereof, wherein the front vehicle body frame assembly 221 is formed by connecting the lower vehicle body frame 203 to the down tube 211 and the front member 212.
The above-mentioned conventional vehicle body frame 201 is largely of a structure bisected into the upper vehicle body frame 202 and the lower vehicle body frame 203, in which the cushion brackets 204 for mounting suspension arms on the left and right sides are mounted bridgingly between the upper vehicle body frame 202 and the lower vehicle body frame 203. In this case, it is considered that the mounting accuracy of the cushion brackets 204 cannot be secured in some cases, depending on the dimensions of the down tube 211 and the front member 212 on the side of the upper vehicle body frame 202 and the dimensions of the left bottom frame 215 and the right bottom frame 216 on the side of the lower vehicle body frame 203.
As shown in Japanese Patent Laid-open No. Sho 63-170176, the cushion brackets 204 are members to which the suspension arms are attached, and, therefore, the cushion brackets 204 are required to be mounted with a high accuracy, so as not to influence the wheel alignment of front wheels.
Also, though not shown in the figure, a steering shaft for steering the front wheels is generally supported at upper and lower two positions of the vehicle body frame. For example, in the case where support portions for the steering shaft are provided respectively on the side of the upper vehicle body frame 202 and on the side of the lower vehicle body frame 203 in the figure, the arrangement in which the support portions are not present on the same frame side makes it difficult to enhance the mounting accuracy of the steering shaft. The mounting accuracy of the steering shaft relates to the steering force on the steering handle, the steering angle of the front wheels, and the like, so that an enhancement of the mounting accuracy is demanded.
Also, in the conventional structure, the cushion brackets 204 are mounted to the upper vehicle body frame 202 and the lower vehicle body frame 203 leads to an increase in the number of mounting steps, as compared with a structure in which the upper vehicle body frame 202 and the lower vehicle body frame 203 are simply connected to each other.
Accordingly, it is an object of the present invention to improve a vehicle body frame structure for an ATV, so as thereby to enhance the mounting accuracies of suspension arm support portions and a steering shaft support portion in a vehicle body frame and to reduce the number of steps for mounting the vehicle body frame.
In general, a vehicle body frame structure for an ATV, wherein the rear wheels are supported by double wishbone type independent suspensions, has been known. Such is disclosed, for instance, in Japanese Patent No. 3069309, wherein a vehicle body frame includes a left-right pair of lower tubes having rear portions so bent as to rise upwards, a cross tube disposed bridgingly between the lower tubes, a left-right pair of rear upper tubes connected to the rear ends of the lower tubes, a left-right pair of rear tubes disposed on the rear side of the lower tubes and each having one end connected to the rear upper tube and the other end connected to the cross tube, and a left-right pair of connection tubes connected respectively to the lower tubes and the rear tubes. In addition, upper arms are vertically swingably mounted respectively to the left and right connection tubes, tension rods are swingably mounted respectively to lower portions of the left and right tubes, and rear wheels are mounted to the bottom ends of the upper arms and the tension rods through knuckles.
One problem with this disclosure is that the upper arms are supported by upper arm support portions provided in the connection tubes, and the tension rods are supported by tension rod support portions provided at lower portions of the lower tubes. In this case, the upper arm support portions and the tension rod support portions are portions for supporting the rear wheels through the upper arms and the tension rods, and are members influencing the wheel alignment of the rear wheels, so that they need higher positional accuracies.
Also, the portions of the vehicle body frame which do not need high accuracies are easier to assemble. Therefore, when the vehicle body frame is divided into the portions needing high accuracies and the other portions, both accuracy and assemblability can be enhanced at the time of assembling the vehicle body frame.
Thus, it is an object of the present invention to enhance positional accuracy of suspension arm support portions and to enhance assemblability of an ATV vehicle body frame.
In general, a cover for covering a lateral side of an ATV, such as a fuel tank cover, a front fender, and a rear fender, have been know. Such is disclosed, for example, in Japanese Patent No. 3358876
FIG. 1 of Japanese Patent No. 3358876 will be described referring to FIG. 22 below. FIG. 22 is a side view of a conventional ATV. The ATV 212 comprises a fuel tank cover 806 covering a lateral upper side of the power unit 804; a front fender 807 covering a front lateral side of the engine 802; a rear fender 808 covering a rear lateral side of the power unit 804; and an opening portion 811 defined by the fuel tank cover 806, the front fender 807, and the rear fender 808.
It may be desired to make the opening portion 811 smaller for further enhancing the aesthetic quality as viewed from a lateral side of the vehicle. However, when the opening portion 811 is made smaller, it negatively affects the maintainability of the engine 802 and the transmission 803.
In view of the above, the fuel tank cover 806, the front fender 807, and the rear fender 808 may be detached at the time of maintenance, whereby the maintenance property can be secured though the opening portion 811 that is small. However, the work for detaching the fuel tank cover 806, the front fender 807, and the rear fender 808 would be troublesome.
In addition, the fuel tank cover 806, the front fender 807, and the rear fender 808 are desired to be enhanced in rigidity so that they will not show resonance upon vibrations at the time of running of the vehicle or due to engine vibrations, for example.
Thus, it is an object of the present invention to improve a side cover for an ATV, thereby enhancing the maintainability of a power unit, particularly an engine, and enhancing the rigidity of the side cover.